The sheer presence of 'std::gmtime' or 'std::localtime' gives rise to C4996 warnings in Microsofts compilers. Alas, the 'fallback(internal::null<>)'functions containing these library calls are never ADL-picked in the respective 'handle(internal::null<>)' selectors. Therefore hiding the fallbacks from msvc is perfectly fine.
std::back_insert_iterators model the OutputIterator concept but differ considerably in their traits and behavior. In particular the former made compilation to fail when format_to_n is given a back_inserter as first argument. The emulation of an OutputIterator is not perfect due to the behavioural differences of back_insert_iterators (e.g. assignment always implies increment) but good enough to be used within fmt's machinery.
change total specialization of 'struct formatter<std::tm>' into partial specialization 'template <typename Char> struct formatter<std::tm, Char>', backed by matching 'strftime'-like overloads
Daniela Engert